However, it has previously been realized that another, simpler method of opening the caps is possible, viz. by a downwards finger pressure against the central area of the cap. This method of opening can be used when the cap is previously prepared in the simple manner that the downwardly projecting cap skirt is provided with three or more slits placed along the circumference of the cap. The skirt portions which cooperate with the bottle head will hereby appear as segments of e.g. 120.degree. or 90.degree., and if the top surface of the cap is just slightly domed, it will be obtained through the downward pressure on the central area of the cap that the individual segments are swung outwards from their engagement with the bottle neck, such that the cap is loosened from the bottle with no need for a usual cap opener.
This would be a particularly attractive opening method, but it has been observed that the slits of the cap skirt diminish the ability of the cap to resist a positive pressure in the bottle to such an extent that this technique has not been usable in practice. Most bottled products are subject to a considerable positive pressure in the production phase, and the caps should also be able to resist such positive pressure in the bottles which may occur later on, e.g. by climatic heat.